In recent years, in order to form an image having excellent water resistance, solvent resistance, scratch resistance, or the like, a photocurable ink composition has been used. The photocurable ink composition contains a photopolymerizable compound and a photopolymerization initiator. Such an ink composition is applied to a recording medium and is then irradiated with light with the result that the photopolymerizable compound contained in the ink composition is polymerized to solidify ink, thereby forming an image (performing printing). However, in the case where several types of conventional photocurable ink compositions are used to perform multicolor printing (hereinafter referred to as “overprinting”, where appropriate), blurring and mixed color (hereinafter referred to as “bleeding”) may be caused at a boundary between the individual inks. An image-forming method has been accordingly studied, which enables the occurrence of the bleeding to be prevented and in which multicolor printing is employed.
For example, Patent Literature 1 discloses a technique in which a color ink is applied after a white ink has been completely cured.
In addition, Patent Literature 2 discloses a technique, in which a white ink is used as a background color in surface printing and reverse printing and in which the conversion rate (rate of a polymerization degree, assuming that a polymerization degree of the ink system in an entirely cured state is 100) of the white ink is set to 30% or higher with the result that the bleeding of the white ink and color ink is prevented.
In addition, Patent Literature 3 discloses an ink jet recording method including: a process of ejecting an ink composition A onto a recording medium, the ink composition A containing a (a-1) polymerization initiator and a (b-1) polymerizable compound which contains N-vinylcaprolactam, and the (b-1) polymerizable compound having a monofunctional polymerizable compound in an amount of 65 weight % or larger with respect to the total weight thereof; a process of exposing the ink composition A to activating radiation to cure the ink composition A; a process of ejecting an ink composition B onto at least part of the cured ink composition A, the ink composition B containing a (a-2) polymerization initiator and a (b-2) polymerizable compound, and the (b-2) polymerizable compound having a polyfunctional polymerizable compound in an amount of 50 weight % or larger with respect to the total weight thereof; and a process of exposing the ink composition B to activating radiation to cure the ink composition B.